The invention relates, in general, to metal forming and, more particularly, to an improved ring rolling mill for rolling rings.
West German Pat. No. 703,436 discloses a ring rolling mill having a main roll and several mandrel rolls mounted on a turntable, and supported by bearings at both ends, which cooperate successively with the main roll. One of the bearings is removable to be able to introduce and remove the workpiece. The mandrel with one bearing or the one bearings with their bearing journal are displaceable in axial direction successively by a drive with automatic control derived from the movement of the turntable. In this known design, the various mandrel roll parts are each mounted in a carriage. The carriage is axially displaceable on the turntable and contains a pressure cylinder. A piston rigidly connected with the turntable is arranged in each cylinder.
This known ring rolling mill is expensive and heavy. Since the turntable absorbs the full rolling force, it lacks rigidity and the accuracy in the dimension and form of the rolled rings cannot meet today's requirements.
Adjustment of the rolls is effected by the rotation of the turntable by a fixed amount, so that unavoidable volume tolerance of the ring blanks used manifest themselves as diameter tolerances of the rolled ring, which leads to further inaccuracies.
Finally, the continuous rotation of the heavy turntable, in contrast to a stepwise movement of the turret head, on the one hand, results in a relatively long station time, while on the other hand, the introduction of the ring blanks becomes more difficult, particularly when automatic devices are to be used for this purpose.
West German Pat. No. 469,226 describes a ring rolling mill, characterized as a tire mill, where the main roll is arranged on an adjustable carriage. German published patent application DOS No. 2,615,802 discloses a ring rolling mill of a different class.